Interesting. Back in the day, although there were a lot of small manufacturers, the choice in the UK was basically Bron, Bowens or Elinchrom when it came to generator flashes.
Patrick Lichfield, the Queen's cousin, had Bron, but then he could afford to
Bowens was known for their engineering quality, they had their own metal shaping/forming machinery and everything was made from sheet steel and built to last, but they weren't too keen on product development and new innovation. Elinchrom weren't made as solidly but were pretty good, and had much better flash performance. I moved over to Elinchrom in the 90's.
From memory, the Bowens Quadmatic had slow recycling, long flash durations and wild colour shifts at different power settings. The main problem though was with the connectors, where the heads plugged into the generator unit. The problem started with mild hissing and crackling noises, which would get worse over time, and which would then develop into serious electrical arcing inside the connectors. Eventually, there would be a dramatic and expensive bang. The problem reminded me of the old distributor points on cars of that era, where arcing would occur and wreck the contact points, but there was a difference because a new set of points could be bought anywhere for very little money, and fitted in 10 minutes . . .
The Estime was meant to be a new model, but I think, again from memory, that the performance was even worse. "Estime" may have stood for "Estimated time until ready to fire" and I think that its main selling point is that, in theory at least, it could be run from car batteries, with even slower recycling.
And, finally, 3000j was very middle of the road back then. Compared to modern units, the output was probably much lower, partly because of resistive losses from the connecting cables. Back then, many pro studio photographers were shooting on large format cameras, usually at f/45 - f/90 and ISO 50 or 100, so high power was needed. I remember that I had 6x Elinchrom 2400j flashes, a 6000j and a 1500j flash, plus a few 600j ones. Those days have gone.